Blass didn't reveal where he got the information, but September 9 is around the same date last year when preorders for the iPhone 6S and iPhone 6S Plus started, namely September 12. Blass' suggestion to "extrapolate the launch event date from there" is easy enough since iPhone sales typically kick off a week after preorders start. On Saturday, Blass already offered a tip via Twitter that the iPhone 7 will launch Friday, September 16.

Analysts and other Apple watchers will be paying close attention to preorder and launch weekend numbers for the iPhone 7. Apple's smartphone sales have declined the past two quarters, leaving the company stuck trying to find a way to boost demand. Many reports say this year's model will offer only modest changes and that Apple is saving major enhancements for next year's edition, but that is all speculation based on limited knowledge.

The rumored new features include stereo speakers, a larger camera lens and dual camera lenses for the iPhone 7 Plus. But another new report suggests Apple may have something up its sleeve for the iPhone 7's home button.

The home button for the new phone will be flat, flush with the surface of the screen, according to Japanese blog site Makotakara. Rather than being the traditional physical button of iPhones past that gives when you press it, the new button would simply respond with a vibration when touched. That could open the door for a 3D Touch-type feature to make its way to the home button.

A September 9 preorder date would mean that Apple's launch event for the iPhone 7 would likely take place the week of September 5. Last year's launch event occurred September 9, a few days before preorders began. September 5 is Labor Day, so that wouldn't work. And unless Apple holds the iPhone 7 event earlier in the month, it will probably take place September 6 or 7.